Multiple revolution type logarithmic volume unit



y 2, 1967 TAKAO MATSUM C JTQ 3,317,877

MULTIPLE REVOLUTION TYPE LOGARITHMIC VOLUME UNIT Filed Jan. 19, 1965 PRIOR ART V F HG 2 munmnnmlllllllllllllmmummllllIillllllllllllmmmllnmmmlllllllmmmml PRIOR ART FIG.3

A B I mmmllllllllllllllllllllllllllm W g FIG.5

United States Patent 1 Claim. 61. 338-89 This invention relates to a novel logarithmic volume unit capable of a multiple revolution operation and has for an object the provision of a volume unit having a logarithmic characteristic of several digits.

A further object of this invention is to provide a high accuracy logarithmic volume unit capable of a multiple revolution operation to provide logarithmic character istics of any desired number of digits.

A still further object of this invention is to provide a novel logarithmic volume unit which is easy to manufacture and maintain.

The multiplerevolution type logarithmic volume unit embodying the principle of this invention comprises a pair of coaxial annular volume sections each including an annulus of an insulating material, a resistance wire wound upon the annulus to provide a logarithmic characteristic, and a sliding arm slidably engaging the resistance. The arms of both sections are secured to a rotating shaft at the same angular position. The two sections are positioned relative to each other in such a manner that their portions of the maximum resistance value are displaced by 180 so that the portion of the maximum resistance value of one section is disposed at the same angular position as the portion of the minimum resistance value of the other section, and the ratio between the widths of the minimum and maximum resistance portions of each of the sections is selected to be equal to 1:3.162. With such a low ratio it is easy to provide an accurate logarithmic characteristic.

While the specification concludes with a claim particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention will be better understood from the following description taken in connection with the accompanying drawing, in which:

FIG. 1 shows a conventional wound type volume unit having a logarithmic characteristic of one digit, with the winding portion being developed over the entire angle of revolution of 360;

FIG. 2 shows a conventional wound type volume unit having a logarithmic characteristic of three digits with its winding portion developed over the entire angle of revolution of 360 corresponding to the logarithmic characteristic of three digits;

FIG. 3 is a developed view of a volume unit embodying this invention wherein the winding portion is divided into two sections at a point corresponding to a point m in FIG. 1, and the divided sections are wound on separate frames;

FIG. 4 is a diagrammatic side View of a volume unit embodying this invention and FIG. 5 is a connection diagram illustrating the relationship between a volume unit of this invention and an external circuit when the volume unit is used in a logarithmic recording meter.

In one example of recording a logarithmic characteristic of several digits, the input is usually applied to a conventional recording meter of a linear characteristic via an amplifier having a logarithmic characteristic of several digits. However, this type of recording is limited to at most three or four digits, and the utilization of a logarithmic amplifier results in much difliculty with regard to Patented May 2, 1967 the accuracy, maintenance, and cost thereof. In another system, a logarithmic volume unit as shown in FIG. 2 is utilized in a logarithmic recording meter to provide the desired records. In the logarithmic volume unit of the type shown in FIG. 2, a length of resistance wire is wound upon a saw-tooth shaped frame of a suitable insulator material in such a manner that the resistance values of two adjacent sections are different by one digit. This construction is also limited to at most approximately three digits and is also disadvantageous in its accuracy, manufacturing, and cost.

The conventional logarithmic volume unit comprises an annulus of a thin sheet of an insulator and a resistance wire of a suitable resistivity densely wound around said insulator annulus. When an accurate logarithmic characteristic as shown by a solid line over a range of the angle of revolution as shown in FIG. 1 is provided, the ratio between the maximum width and the minimum width will be about 10:1. However, as the maximum width is limited by the dimensions of the volume unit, the width thereof will be limited over the entire angle of revolution so that the minimum width will become too narrow, thus making it difiicult to manufacture and maintain the volume unit. Therefore, in practical units, the width of the narrow portion thereof is widened as shown by dotted line in FIG. 1. Furthermore, as the slope of the logarithmic characteristic curve near the maximum width becomes large, the turns of the resistance winding have a tendency to displace, and hence .the turns make an angle to the vertical line. This greatly affects the accuracy of the unit.

In accordance with this invention, the volume unit is divided into two sections at a point In corresponding to an angle of revolution of as shown in FIG. 1. More particularly, FIG. 3 shows these two sections A and B, respectively corresponding to sections a -m and m-d in FIG. 1. When measured on the solid characteristic curve shown in FIG. 1, the ratio between the widths at points a and m of the section A is 13.162, and the ratio between the widths at points, m and d of the section B is 3.162: 10. These ratios of both A and B are equal and are considerably smaller than said ratio 1:10. Moreover, the configurations of the sections A and B are identical or proportional. While these sections are formed by winding resistance wires of different diameter and resistivity, it is possible to make substantially equal the widths of the sections A and B by adopting an appropriate design. Thus, by dividing the volume unit into two identical sections, the accuracy, manufacture and maintenance thereof can be greatly improved.

Also this divisional construction provides volume units of a multiple revolution type. In the conventional volume unit, the opposite terminals of the resistance winding is spaced by a gap so that they may not be short circuited by the sliding member, whereby the effective angle of rotation is decreased to about 350, and hence it is impossible to give the multiple revolution characteristic to the volume unit of this invention. The section A covers a range of the angle of revolution of from 0 to 180, while the section B covers that from 180 to 360, and since these two sections can be positioned 180 out of phase, the portion of the winding corresponding to the point a of the section A FIG. 3 is positioned close to the portion of the winding corresponding to the point d of the section B. Since the sliding members of sections A and B assume the same angle of revolution at any regular position at the time of transition from one digit to another, in other words at an instant of transition from the point a of the section A or from the point d of the section B to the succeeding region, both sliding members are in contact with their associated windings. This apparently results in short circuiting, but actually this can be avoided by connecting the volume unit to be activated in an external circuit as shown in FIG. 5 instead of interconnecting the two sections inside the unit.

As shown in FIGURE 4, sections A and B are disposed coaxially in a casing 10. Each of the sections A and B comprises an annulus of insulator sheet 11, a length of resistance wire 12 wound on the annulus to provide the desired logarithmic characteristic as above described, and a sliding member or arm 13. Arms 13 of both sections are secured to a rotating shaft 14 at the same angular position. As can be clearly noted from FIG. 4, the points b and d of the maximum resistance value of the sections A and B are displaced relatively by 180 so that the portion of the maximum resistance value b of the section A is positioned at the same angular position as the portion 0 of the minimum resistance of the section B.

Although'the logarithmic volume unit per se of this invention has a logarithmic characteristic of one digit, by switching the digits of a logarithmic type recording meter at switch member SW, it is possible to smoothly transfer from the maximum value to the minimum value or vice versa in a logarithmic characteristic of one digit of the logarithmic volume unit so that the transfer can be made continuously for any member of revolutions, thus providing the function of multiple revolutions.

In the conventional logarithmic volume unit of one digit, a point corresponding to the point 1 in FIG. 1 is positioned at an angle of revolution of about from 30 to 40 measured from the reference point a, and the resistance value of the portion between points a and 1 is corrected after manufacture, but the attainable accuracy is only about -0.5%. In contrast, when the volume unit is made as shown in FIG. 3 in accordance with this invention, correction can easily be effected to provide an accuracy of $0 .2% over the entire angle of revolution. It is expected that higher accuracy can be provided by superior technique in manufacturing. It is possible to manufacture logarithmic recording meters of multiple digits by utilizing the logarithmic volume unit of this invention thus making possible recording over a Wider range than with the conventional recording meters. Moreover, it is possible to obtain comparative records in every digit which are convenient for direct reading necessary for overall judgment. 7

While the invention has been explained by describing a particular embodiment thereof, it will be apparent that improvements and modifications may be made without departing from the scope of the invention as defined in the appended claim.

What is claimed is:

A multiple revolution type logarithmic volume unit having two volume sections, each section including an annulus of insulator sheet, a resistance Wire Wound on said insulator sheet over an angle of for providing a logarithmic characteristic and terminals for said resistance wire, a minimum resistance position of one of said sections corresponding in an axial direction to a maximum resistance position of the other of said sections, a casing, said annuli being stationarily and coaxially supported by said casing to be in side by side relationship in an axial direction, a rotatable shaft mounted in said casing in coaxial relation to said volume sections, contact arms on said shaft cooperable with the resistance wires of the respective sections, said arms 'being positioned on said shaft at the same angular position, a minimum resistance terminal of one section being connected with a maximum resistance terminal of the other of said sections, a logarithmic recording meter having a switching part for the digits thereof, and said contact arms being connected to said switching part.

References Cited by the Examiner UNITED STATES PATENTS 1,496,745 6/1924 Scott 33889 2,615,065 10/1952 Farnham 33889 2,720,572 10/1955 Moore 33-8-90 2,850,604 9/1958 Rowley 33889 2,938,184 5/1960 Mayer 338-89 3,046,510 7/1962 Williams et al. 33889 RICHARD M. WOOD, Primary Examiner.

W. D. BROOKS, Assistant Examiner. 

